The justices on Monday agreed to hear an appeal from abortion opponents, who wanted the law thrown out. The law allows individuals to enter the buffer zone only to enter or leave the clinic or reach a destination other than the clinic.

Abortion opponents who regularly stand outside clinics in Boston, Worcester and Springfield claimed the law unfairly keeps them from engaging patients in conversations at a closer distance.

The 1st U.S. Circuit Court of Appeals upheld the law, saying it protects rights of prospective patients and clinic employees "without offending the First Amendment rights of others."